1. Field of the Disclosure
The disclosure generally relates to valve actuated writing instruments including ink compositions having large pigment particles and more particularly to poppet valves for such writing instruments.
2. Related Technology
Known writing instruments generally include an instrument body or shell, an ink reservoir containing an ink composition within the instrument body, and a writing tip or nib in fluid communication with the ink reservoir to deliver the ink composition to a substrate. Some writing instruments, such as ball point pens, contain relatively non-volatile, high viscosity inks. The ink compositions of these writing instruments generally contain relatively small pigment particles to avoid clogging the ball point or other delivery system. As a result, these writing instruments are generally limited in the type of ink that can be delivered to a substrate. On the other hand, such writing instruments containing viscous, non-volatile inks have little need for sealing mechanisms because there is little danger that the ink will evaporate under normal conditions.
Writing instruments such as capillary-action markers typically contain more volatile and less viscous inks. Conventional capillary-action markers contain a fibrous ink reservoir and a fibrous nib in fluid communication therewith. Such markers typically include an ink composition having a relatively low viscosity because the adhesive forces (between the ink composition and the channel walls of the reservoir and/or nib) must exceed the cohesive forces of the ink composition to permit movement of the composition by capillary action. Incorporating pigment particles such as aluminum flakes into the low viscosity ink compositions of a capillary-action marker is difficult because such pigment particles tend to settle out and agglomerate within the reservoir, nib, or both, rendering the marker inoperable. Even when the pigment particles are adequately suspended in the ink compositions, the marker's delivery system (e.g., the fibrous ink reservoir and the fibrous nib) typically undesirably becomes clogged over time. Thus, the pigment particle size in such systems is limited.
More recently, valve-action markers containing relatively large pigment particles have been developed. Typically, such valve-action markers utilize a spring-loaded nib, which opens a valve to an ink reservoir when depressed in the axial direction (e.g., against a writing surface), thereby allowing the ink to flow from the ink reservoir to the nib. Such valve-action markers are problematic, however, in that the pigment particles tend to settle to the bottom of the ink reservoir when the valve-action markers are not in use. Therefore, a consumer typically has to violently shake the marker prior to using same in order to effect distribution of the pigment particles throughout the ink composition and ensure that the ink composition delivered to the marker nib contains sufficient amounts of pigment particles to produce the desired visual effect. However, the consumer typically has no means to verify that the pigment particles material has been adequately distributed throughout the ink composition because the marker barrel or shell is opaque. The user must also subsequently depress the nib against a writing surface with significant force to open the valve to the ink reservoir and continue to apply significant force on the nib in order to allow delivery of the ink composition to the nib when writing. The valve of such systems typically must be moved substantially, typically 0.1 inches or more, in an axial direction before ink will begin to flow. This large axial movement must be repeated and maintained whenever ink is delivered and is therefore generally undesirable from the standpoint of consumers. In fact, such a large valve displacement requires a relatively heavy force that can significantly exceed the forces generated during normal writing. Thus, known valve systems require a consumer to use an unnatural writing stroke which can be fatiguing.